ELECTROCHEMISTRY OF THIOBACILLUS-FERROOXIDANS INTERACTIONS WITH PYRITE

A cyclic voltammetry technique was used to study the interactions of mineral-pyrite during bioleaching with the bacterium Thiobacillus (T.) ferrooxidans over its entire growth cycle. Invariably, the pyrite surface drastically changed its properties on the second day of bacterial growth (bioleaching). After 2 days, the cyclic voltammograms (CVs) were insensitive to convective diffusion produced by stirring. The product layer was examined by scanning electron microscopy (SEM), X-ray diffraction, and chemical analysis. The SEM study revealed an extremely high density of bacteria on the pyrite surface. The high density of bacteria, along with the solid reaction products formed on the pyrite surface, created conditions for crack/pore diffusion, explaining why the CVs became insensitive to convective diffusion (stirring) in solution. X-ray diffraction study confirmed jarosite as a product layer. A mechanism is proposed by which T. ferrooxidans cells serve as nucleation sites for jarosite formation.